Opacifying agents for enamels and glazes



Patented June 20, 1939 PATENT forr cr.

OPACIFYING AGENTS FORENAMELS 'AND GLAZES Ludwig Weiss, Frankfort-on-the- Main, Germany,

assignmto Deutsche Gold and Silber Schelde- I Anstalt, vormals R'oessler, Frankfort-on-the- Main, Germany, a corporation of Germany No Drawing. Application January 5, 1938, Serial No. 183,517. In Germany December 9, 1936 I 9Claims. 'wl. loo-sea).

This invention relates to certain'opaciilers for opacifying enamels and glazes. More particularly, it relates to certain opacifying agents which, when introduced into enamels or glazes.

:I impart thereto a white, opaque color. It is also concerned with a method of utilizing the novel opacifying agents to produce white opaque glazes.

At present the oxides of zirconium,"titanium, tin, and antimony 'are'in extensive use as enamel opacifiers. The opacifying agents with which this invention is concerned, the basic sulfates of cerium with various degrees of hydration, possess definite advantages over the metallic opaciflers named.

In accordance with. the present invention I utilize as the improved opacifying agents basic sulfates of cerium having various degrees of hydration which may be represented generally by the formula 4CeOz-a'SOs-z/H2O. As examples 2o may'be given the basic sulfates having formulae ranging from 4Ce0z- SOa-mOto 4Ce0a- 3S0: H20.

Hydrated basic sulfates ofintermediate'composition are also utilizable.

These hydrated basic cerium sulfates possess an extraordinarily high opacifying effect when introduced into enamels and glazes. Relatively small amounts of the novel opacifying agents are sufllcient to secure an opacity in the enamel of superior density and satisfactory whiteness.

It is possible to prepare the basicsulfates which I utilize for opacifying enamels and glazesby treating a suspension of cerium hydrate with an equivalent .amount of sulfuric acid, separating the solution, and dryingthe solidresidue. If desired, the product may be heated sufliciently to expel more or less of thewater of hydration. Water of hydration maybe expelled by heating in suillclent amount to form any desired final Product.

In addition to the basic-sulfates of cerium,

' small amounts of other basic compounds such as the alkali metal or alkaline earth metal salts of silicic 'acid, or the aluminum salts of silicic acid may also be incorporated inthe opacifler. If

desired, mixtures of'the various alkali metal and alkaline earth metal salts of silicic acid, as well as aluminum silicate, may be employed in conjunction with the basic sulfates of cerium. For example, water glass (sodium silicate) may be advantageously added to the hydrated basic sulfate of cerium oxide which is utilized as the opacifying agent. I

The opacifying effect of the hydrated basic sulfates is at least equivalent to that of. stannic l6 oxide. For example, 2% of the basic sulfates as prepared.

described will give substantially the same opaquing effect as 2% of stannic oxide. This is indeed remarkable as the hydrated basic sulfates,

.when present in the amount of 2% in the mill frit, impart thereto less than 1% of ceric oxide 5 (CeOa).'

As an example of the use of my novel opacifying agents, the following may be given:

- Example 10 An opacifying agent of the type described having a composition, by weight, equivalent to 47.6 parts of CeO:, 17.3 partsv of S03, 8.3-parts of S102, 2.5 parts of NazO and 24.3 parts of H10 was a 200 grams of this opacifying agent 16 was then ground in a ball mill with 10 kilograms of a frit having the composition:

. Parts S102- 51.55 AIQOIL. V 8.50 20 CaFz 1.75 NaaAlFa; 14.60 Na2B4O7 13.15 Nit-20--.... 6.80 K:O a 3.65 25 The product was then mixed with 6% of enamelling clay, applied in the usual way to a twice treated metal sheet containing a ground enamel coat, and fired. The opacifying effect obtained in this manner with.0.95% of cerium oxide was 30 substantially equivalent to the opacifying effect obtained with 2% of stannic oxide. I

It should be understood that the various details hereinbefore given are to be regarded as illus-I trative and not restrictive, the scope of'my in- 35 vention' being determined in accordance with the appended claims.

- I claim: I I

1. An enamelfopacifying'agent comprising a basic sulfate-of cerium having a formula ranging from 4CeOz-SOq-Hz0 to 4CeOz-3SOa-Ha0. together with oneor more of the basic silicates. selected from the group consisting of the alkali metal silicates, the alkaline earth metal silicates and thealuminum silicates. I

2. An enamel opacifying agent which comprises a hydrated basic'sulfate of cerium and'an alkali metal silicate. I

3. An enamel opacifying agent which coniprises a hydrated basic sulfate of cerium and one or more of the basic silicates selected from the group which consists of the alkali metal silicates, the alkaline earth metal 'silicates and the silicates of aluminum. I 1

4. A method of opacifying an enamel or glaze which comprises incorporating therein a small amount of a hydrated basic sulfate of cerium.

5. A method of opacifying an enamel or glaze which comprises incorporating therein a small 5 amount of a hydrated basic sulfate of cerium having the formula 4CeOz-xSO3-1/Hz0.

6. A method of opacifying an enamel or glaze which comprises incorporating therein a small amount of a hydrated basic sulfate of cerium 10 having a composition ranging from that represented by 4CeO:-SO:-H2O to that represented by 4CeOz-3S0s'H20.

7. A process as defined in claim 6 wherein there is present, in addition to the hydrated basic sulfate of cerium. a small amount of a basic compound of an alkali metal or alkaline earth metal or of aluminum, or two or. more of said basic compounds. I i I 8; An enamel opacifylng agent comprising a hydrated basic sulfate of cerium and a small amount of a basic compound of the alkali metals, alkaline earth metals or of aluminum or two or more of these basic compounds.

9. An enamel opacifler as defined in claim 8 which comprises siliclc acid or a salt thereof.

LUDWIG WEISS. 

